Kippei Katakura is a high school playboy who would flirt with any girl he sees. His life was turn upside down when one day, his 5-year old cousin Yuzuyu shows up at his house after her mother had seemingly abandoned her. And now, Kippei has been handed the task of taking care of Yuzuyu for the time being, and he must learn how to become the “mother” that Yuzuyu needs.